net: iosm: remove the repeated declaration and comment

Function 'ipc_mmio_get_cp_version' is declared twice, so remove the
repeated declaration and wrong comments.

Cc: M Chetan Kumar <m.chetan.kumar@intel.com>
Cc: Intel Corporation <linuxwwan@intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Shaokun Zhang <zhangshaokun@hisilicon.com>
Reviewed-by: M Chetan Kumar <m.chetan.kumar@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>